This invention relates generally to a tone hole covering assembly for wind instruments and to a novel pad cup and retainer which allows adjustment of the pad without causing damaging stress on the pad or pad cup-retainer combination. Although generally applicable to all wood-wind instruments, one embodiment of the tone hole covering assembly or pad assembly is especially suited for use in clarinets and the novel pad cup and retainer are especially suited for use in flutes.
During this century, instrument pads have typically comprised a cardboard backed wool felt disk covered with Goldbeater's skin, wrapped around the cardboard and glued to its backside. The pad is fixed in a pad cup, sealing side exposed, and the combination mounted over an instrument tone hole on a hinged mechanism so that the tone hole is sealed when the pad is in its closed position. Typically, the back or hinged side of the pad remains closer to the tone hole in the pad's open position. The inability of the tone hole to close tightly with minimal pressure affects the instrument's tone and the player's technique. An instrument pad only 0.001 of an inch out of adjustment produces an air leak detectable by the player.
Although this pad can initially be made to seal well, it needs frequent adjustments or replacement when subjected to changes in humidity, temperature, and altitude. Under humid conditions, the felt, composed of wool fibers, adsorbs moisture from the atmosphere causing the entire pad to expand. When the player depresses such a pad, its back touches the tone hole first leaving a gap in front where air leaks. Under conditions of low humidity, the felt pad releases moisture causing the entire pad to shrink. As a result, the pad, when depressed normally, will touch the front of the tone hole first, leaving a gap at the back where air leaks. Changes in temperature or altitude similarly cause changes in the felt backing. To further complicate matters, the skin similarly expands and contracts depending on its environment. This lack of dimensional stability of the felt and skin causes the pad surface to loose its integrity and is the primary cause of air leaks at the pad-tone hole interface.
Finally, the felt backing typically exhibits a variable density or distribution of fibers. In the areas having fewer fibers, soft spots occur where the felt cannot adequately support the skin. Shrinkage of the skin and usage compress these areas more than surrounding areas. As a result, the skin is no longer held to the tone hole and air leaks develop at the pad-tone hole interface.
Regardless of the source of small air leaks, the player can usually compensate by applying more pressure against the pad at the expense of his technique. As the leaks become more severe, the player can no longer compensate and his tone and response suffer.
In 1987, in U.S. Pat. No. 4,704,939, a new pad was disclosed that can maintain a flat sealing surface regardless of variations in temperature, moisture, or altitude. As a result of this design, pad life is extended and closure of the tone hole consistently requires only a light touch by the musician. To accomplish these advantages, the new pad has a semi-rigid supporting unit for the felt. The pad's design allows its surface to be tilted to fit a tone hole with a perfectly planar surface through the leveling process of triangulation or, by a wedging action, to distort the planar surface to perfectly match a damaged or imperfect tone hole. Both leveling techniques may be used on the same pad.
The new pads are constructed by stretching a skin across a cushion ring fitted within a recess on the lower radial face of a rigid backing disk having a bendable lower margin. The skin is folded around the edge of the backing disk and secured to the disk's back side. The pad is secured to its cup with a retainer comprising a flat washer and screw combination attached to a pad nut which is in turn attached to the bottom of the pad cup and centrally located within the cup's cavity. Alternatively, the backing disk having a threaded hole centrally located to secure the flat washer and screw combination can be secured to the cup with an adhesive. As before, the flat washer and screw combination secures the pad within its cup. One embodiment of the improved pad allows for further adjustment by bending or flexing the pad or a portion of the pad with a specially designed tool. A second embodiment of the new pad allows for further adjustment by placing complete or partial shims between the rigid and bendable portions of the backing disk. When partial shims are used and the screw holding the flat washer against the sealing surface is tightened, a wedging action occurs that exerts pressure against the bendable margin of the backing disk. The pressure exerted causes the backing disk to bend or flex and conform to the surface of the tone hole. Additional information regarding the design and methods for adjusting the sealing surface of these pads is described in U.S. Pat. No. 4,704,939, the disclosure of which is hereby incorporated by reference.
Inherent in the bending or flexing operation utilized to adjust the pad is the creation of stress on the pad's surface, its retainer, and components of the pad cup. During pad adjustment, more pressure is typically exerted on the more wedged side of the pad surface. As a result, three deleterious effects occur. First, in the region of most wedging, the rigid metal washer presses into the skin making it more taut and increasing its chances of tearing at that point. Second, compression of the pad's surface results as the rigid metal washer opposes the wedging force in the region of maximum adjustment. Finally, as the result of this compression, the pad becomes less resilient in this same region. Each of these effects limit the pad's ability to seal the tone hole with maximum efficiency. The forces created during pad adjustment can also damage components of the pad cup or the pad's retainer. Depending on the amount of wedging required, stress can cause the pad nut to break away from the cup or cause the head of the retainer's screw to break. As will be apparent from the following discussion, this invention provides for a pad cup and retainer capable of withstanding the stress caused by adjustment of the pad because of its greater ability to absorb and dissipate the resulting stress.
Although the pad assemblies of all woodwind instruments suffer from the design limitations or shortcomings described, the design of individual instruments can place additional demands on the pad assemblies. For example, the flute's tone hole with its perpendicular wall is located substantially above the instrument's body and can accommodate a pad having a more exposed outer rim. In contrast, the tone holes for woodwinds with wooden bodies are not perpendicular to the instrument's body, but taper gradually away from the pad's surface. As a result, upon closure of the tone hole, contact between the outer rim of the pad and the wall of the tone hole is more likely to occur, damaging the skin covering the outer rim of the pad and causing a clicking sound. Although a soft pad surface can better conform to the tone hole providing for a better and quieter seal, pads with a soft non-firm felt backing becomes non-planar when the skin covering is stretched over the backing and glued to the back side of the backing disk causing a poor seal.
A preferred pad for a clarinet, a saxophone, or other woodwind instrument would have a felt cushion comprising a soft but firm outer region, a softer region over the tone hole, and a firm central region centered over the tone hole. Such a backing would minimize deformation of the pad's surface because of its improved dimensional stability; allow the pad to remain flat during its lifetime by providing maximum support for the skin covering at the pad's outer circumference; and minimize wear and abrasive damage produced by contact of the pad's outer circumference with cleaning cloths, sharp objects, or the tone hole. In addition, this backing would provide for optimum seal at the tone hole's sealing surface and minimum noise resulting from closure of the tone hole. Finally, the pad's firm central region would optimize tone produced by the instrument.